Reportable Segments (Details) (USD $)	3 Months Ended		9 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014 item	Jun. 30, 2013
Reportable Segments
Number of reportable segments			2
Summarized financial information concerning the Company's reportable segments
Revenue	$ 1,968,155,000	$ 2,067,490,000	$ 5,794,254,000	$ 6,074,408,000
Revenue, net of other direct costs	1,204,700,000	1,236,000,000	3,536,400,000	3,732,900,000
Gross profit	108,540,000	131,814,000	274,145,000	309,775,000
Equity in earnings of joint ventures	5,896,000	4,094,000	49,415,000	17,855,000
General and administrative expenses	(22,904,000)	(24,010,000)	(73,198,000)	(73,365,000)
Operating income (loss)	91,532,000	111,898,000	250,362,000	254,265,000
Gross profit as a % of revenue	5.50%	6.40%	4.70%	5.10%
Gross profit as a % of revenue, net of other direct costs	9.00%	10.70%	7.80%	8.30%
Corporate
Summarized financial information concerning the Company's reportable segments
General and administrative expenses	(22,900,000)	(24,000,000)	(73,200,000)	(73,400,000)
Operating income (loss)	(22,900,000)	(24,000,000)	(73,200,000)	(73,400,000)
Professional Technical Services
Summarized financial information concerning the Company's reportable segments
Revenue	1,794,600,000	1,847,100,000	5,248,400,000	5,384,200,000
Revenue, net of other direct costs	1,112,000,000	1,102,000,000	3,214,700,000	3,306,100,000
Gross profit	99,500,000	119,800,000	244,700,000	281,300,000
Equity in earnings of joint ventures	2,100,000	1,000,000	36,500,000	10,300,000
Operating income (loss)	101,600,000	120,800,000	281,200,000	291,600,000
Gross profit as a % of revenue	5.50%	6.50%	4.70%	5.20%
Gross profit as a % of revenue, net of other direct costs	8.90%	10.90%	7.50%	8.50%
Management Support Services
Summarized financial information concerning the Company's reportable segments
Revenue	173,600,000	220,400,000	545,900,000	690,200,000
Revenue, net of other direct costs	92,700,000	134,000,000	294,700,000	426,800,000
Gross profit	9,000,000	12,000,000	29,400,000	28,500,000
Equity in earnings of joint ventures	3,900,000	3,100,000	13,000,000	7,600,000
Operating income (loss)	$ 12,900,000	$ 15,100,000	$ 42,400,000	$ 36,100,000
Gross profit as a % of revenue	5.20%	5.40%	5.40%	4.10%
Gross profit as a % of revenue, net of other direct costs	9.70%	9.00%	10.00%	6.70%